1. Field of the Invention
The present invention relates to a decorative laminated sheet, particularly to a decorative laminated sheet having excellent moldability, a low temperature impact resistance, surface smoothness, colorless transparency and other various properties; the decorative laminated sheet resists becoming cloudy or opaque when embossing or heat sealing. The decorative laminated sheet of the present invention is particularly suitable for vacuum press molding, pneumatic press molding and membrane press molding.
2. Description of the Related Art
Conventionally, decorative laminated sheets have been widely used or laminated on metallic or wooden materials such as furniture, cabinets, fittings, desks and cupboards. The decorative laminated sheets have been laminated and sealed tightly on adherends having complex contours by the membrane press molding.
For example, Japanese Patent Publication No. 7-39170 discloses a decorative laminated sheet composed of a substrate layer of a polyvinyl chloride sheet and a transfer film laminated thereon using a laminating method of so-called doubling embossing. According to Japanese Patent Publication No. 7-39170, a decorative laminated sheet having stain resistance, scratch resistance and high gloss is provided.
Japanese Patent Laid-Open No. 7-24979 discloses a decorative laminated sheet composed of an opaque polyolefin type resin film and an amorphous polyethylene terephthalate resin film. The amorphous film used for the sheet described in Japanese Patent Laid-Open NO. 7-24979 is partially crystalline. According to Japanese Patent Laid-Open NO. 7-24979 a decorative laminated sheet having excellent moldability, transparency, weather resistance, stain resistance or the like can be obtained.
However, when the above-mentioned decorative laminated sheets are molded by membrane press molding, vacuum press molding, or pneumatic press molding, the sheet may become cloudy or opaque when embossing or heat sealing.
When membrane press molding, a thermoplastic decorative sheet, which is colored or surface-printed with a desired color and a desired thickness, is heated to approximately the softening point thereof, placed on an adherend having a complex contour such as a door of a kitchen unit, covered with, for example, a rubber sheet and then air or liquid pressure is applied to stick the decorative sheet to the contour. Vacuum press molding and pneumatic press molding are based on a same principle of the membrane press molding. The former is a molding method with a vacuum pressure using no membrane rubber, and the latter is a molding method utilizing an air pressure.
The decorative laminated sheet is generally manufactured by a calendar roll method. During the manufacture, irregularities, so-called bank marks, are partially produced caused by a nonuniform flow of a peculiarity of the resin on a calendar sheet. The irregularities do not cause adverse affects on a practical use, however, they affect the smoothness of the surface, resulting in a damaged appearance. In addition, if the line speed is increased when doubling embossing, the bank mark becomes more prominent, thereby reducing productivity.
Moreover, the decorative laminated sheet tends to crack easily at a low temperature. The sheet can crack when handling it in winter.
Furthermore, the sheet composed of the substrate layer of polyvinyl chloride disclosed in the Japanese Patent Publication No. 7-39170 is colored at an early stage, and, due to thermal degradation, is not an especially excellent transparency.
An object of the present invention is to provide a decorative laminated sheet having excellent moldability, a low temperature impact resistance, surface smoothness, colorless transparency and other various properties; the decorative laminated sheet resists becoming cloudy or opaque when embossing or heat sealing, and is particularly suitable for vacuum press molding, pneumatic press molding and membrane press molding.